check root block num before returning it when include_root_t::yes

[spoonincode]

Without this change it's possible for forkdb to return a block that does not match the block number requested which is causing a ship test malfunction.

Consider a forkdb that is rooted at block 300, has a head that is 300, and no block log exists, something calls get_block_id_for_num(299)

spring/libraries/chain/controller.cpp

Lines 5201 to 5208 in 2b1228e

	block_id_type controller::get_block_id_for_num( uint32_t block_num )const { try {
	const auto& blog_head = my->blog.head();
	bool find_in_blog = (blog_head && block_num <= blog_head->block_num());
	if( !find_in_blog ) {
	std::optional<block_id_type> id = my->fetch_block_id_on_head_branch_by_num(block_num);
	if (id) return *id;

so,

spring/libraries/chain/controller.cpp

Lines 1140 to 1142 in 2b1228e

	std::optional<block_id_type> fetch_block_id_on_head_branch_by_num(uint32_t block_num) const {
	return fork_db.apply<std::optional<block_id_type>>([&](const auto& forkdb) -> std::optional<block_id_type> {
	auto bsp = forkdb.search_on_head_branch(block_num, include_root_t::yes);

ultimately,

spring/libraries/chain/fork_database.cpp

Lines 532 to 534 in 2b1228e

	template<class BSP>
	BSP fork_database_impl<BSP>::search_on_head_branch_impl( uint32_t block_num, include_root_t include_root ) const {
	return search_on_branch_impl(head->id(), block_num, include_root);

notice above that the first parameter will be the block id for block 300. then,

spring/libraries/chain/fork_database.cpp

Lines 513 to 516 in 2b1228e

	BSP fork_database_impl<BSP>::search_on_branch_impl( const block_id_type& h, uint32_t block_num, include_root_t include_root ) const {
	if( include_root == include_root_t::yes && root->id() == h ) {
	return root;
	}

since root == head && include_root_t the block id for block 300 will be returned. But we asked for block 299!

[linh2931]

Good catch. Could have a unit test in the future.

[ericpassmore]

Note:start
group: STABILITY
category: INTERNALS
summary: Fix sporadic issues, update ForkDB to return block matching block number.
Note:end